All-optical transistor created

The MPQ/EPFL microresonator, which couples light with vibrations (Photo: EPFL)

Researchers from Germany’s Max Planck Institute of Quantum Optics (MPQ) and the Swiss Ecole Polytechnique Federale de Lausanne (EPFL) have created a microresonator that produces vibrations from laser light. The device also uses one laser beam to control the intensity of another, thus making it essentially an optical transistor. The technology could have big implications in fields such as telecommunications.

The heart of the microresonator is a silica toroid – a tiny circular glass structure with a diameter smaller than that of a human hair. It is supported on a silicon pillar, which is itself part of a semiconductor chip. When a focused beam of light is directed into the toroid, the photons are trapped and guided in a circular pattern, exerting a force known as radiation pressure. This pressure causes the toroid to vibrate, at frequencies 10,000 times higher than those that could be attained in a more traditional structure, such as a wine glass.

When two laser beams are incorporated, the stronger “control” beam acts as an optical switch, controlling whether or not the weaker “signal” beam is able to enter the toroid.

The effect of the microresonator has been dubbed OMIT, or optomechanically-induced transparency. The MPQ and EPFL researchers believe that it could be used for telecommunications applications such as optical buffers, in which optical information could be stored for several seconds. They also see the technology helping in the development of quantum computing systems.

The MPQ/EPFL microresonator, which couples light with vibrations (Photo: EPFL)